U.S. patent application number 16/652988 was filed with the patent office on 2020-08-20 for control device for internal combustion engine.
This patent application is currently assigned to Yanmar Co., Ltd.. The applicant listed for this patent is Yanmar Co. Ltd.. Invention is credited to Kastunari Jonouchi, Hironori Yamane.
Application Number | 20200263625 16/652988 |
Document ID | 20200263625 / US20200263625 |
Family ID | 1000004813723 |
Filed Date | 2020-08-20 |
Patent Application | download [pdf] |
![](/patent/app/20200263625/US20200263625A1-20200820-D00000.png)
![](/patent/app/20200263625/US20200263625A1-20200820-D00001.png)
![](/patent/app/20200263625/US20200263625A1-20200820-D00002.png)
![](/patent/app/20200263625/US20200263625A1-20200820-D00003.png)
![](/patent/app/20200263625/US20200263625A1-20200820-D00004.png)
United States Patent
Application |
20200263625 |
Kind Code |
A1 |
Yamane; Hironori ; et
al. |
August 20, 2020 |
Control Device for Internal Combustion Engine
Abstract
An ECU includes a cooling water temperature sensor, an intake
air temperature sensor, a storage unit, a determination unit, and a
calibration unit. In an after-run control performed after the
internal combustion engine stops, the determination unit compares a
cooling water temperature Tw detected by the cooling water
temperature sensor with a first threshold value T1 and determines
that the environment is not the cold environment in which an EGR
differential pressure sensor is likely to be frozen, if the cooling
water temperature Tw is equal to or higher than the first threshold
value T1, or if the cooling water temperature Tw is less than the
first threshold value T1 but is equal to or higher than a second
threshold value T2 which is lower than the first threshold value T1
and an intake air temperature Ta from the intake air temperature
sensor is equal to or higher than a third threshold value T3, and
determines that the environment is the cold environment otherwise.
When the environment is determined as not to be the cold
environment, the calibration unit obtains a calibration reference
value based on the detection value from the EGR differential
pressure sensor. The storage unit stores the calibration reference
value obtained by the calibration unit.
Inventors: |
Yamane; Hironori; (Osaka,
JP) ; Jonouchi; Kastunari; (Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Yanmar Co. Ltd. |
Osaka |
|
JP |
|
|
Assignee: |
Yanmar Co., Ltd.
Osaka
JP
|
Family ID: |
1000004813723 |
Appl. No.: |
16/652988 |
Filed: |
August 15, 2018 |
PCT Filed: |
August 15, 2018 |
PCT NO: |
PCT/JP2018/030334 |
371 Date: |
April 2, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F02M 26/49 20160201;
F02D 41/22 20130101; F02D 41/2474 20130101; F02D 41/2432 20130101;
F02D 41/2441 20130101 |
International
Class: |
F02D 41/24 20060101
F02D041/24; F02M 26/49 20060101 F02M026/49; F02D 41/22 20060101
F02D041/22 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 30, 2017 |
JP |
2017-209441 |
Claims
1. A control device for an internal combustion engine configured to
calibrate a detected value from a pressure detection unit of the
internal combustion engine, during operation of the internal
combustion engine, the device comprising: a cooling water
temperature detection unit configured to detect a cooling water
temperature of the internal combustion engine; an intake air
temperature detection unit configured to detect an intake air
temperature of the internal combustion engine; a storage unit
configured to store a calibration reference value for calibrating
the detection value from the pressure detection unit; a
determination unit configured to determine whether an environment
is a cold environment in which the pressure detection unit is
likely to freeze; and a calibration unit configured to obtain the
calibration reference value, wherein in an after-run control
performed after the internal combustion engine stops, the
determination unit compares a cooling water temperature detected by
the cooling water temperature detection unit with a first threshold
value and determines that the environment is not the cold
environment if the cooling water temperature is equal to or higher
than the first threshold, if, as a result of the comparison, the
cooling water temperature detected by the cooling water temperature
detection unit is less than the first threshold value; the
determination unit determines that the environment is not the cold
environment if the cooling water temperature is equal to or higher
than a second threshold value lower than the first threshold value
and the intake air temperature is equal to or higher than a third
threshold value, and otherwise, determines that the environment is
the cold environment, the calibration unit obtains a calibration
reference value based on the detection value from the pressure
detection unit when the determination unit determines that the
environment is not the cold environment, and the storage unit
stores the calibration reference value obtained by the calibration
unit.
2. The control device for the internal combustion engine according
to claim 1, wherein if the cooling water temperature detected by
the cooling water temperature detection unit is equal to or higher
than a fourth threshold value within a period after powering on and
before start of the internal combustion engine, the calibration
unit obtains the calibration reference value based on a detection
value detected by the pressure detection unit within the period
after powering on and before start of the internal combustion
engine, and uses the calibration reference value thus obtained to
calibrate detection values of the pressure detection unit after
start of the internal combustion engine, and if the cooling water
temperature is less than the fourth threshold value within the
period after powering on and before start of the internal
combustion engine, the calibration unit uses the calibration
reference value stored in the storage unit, to calibrate detection
values of the pressure detection unit after start of the internal
combustion engine.
Description
TECHNICAL FIELD
[0001] The present invention relates to a control device for an
internal combustion engine, which calibrates a pressure sensor.
BACKGROUND ART
[0002] Traditionally, there has been a known structure that
calibrates a pressure sensor in an internal combustion engine, for
a purpose of correcting an influence on the output of the pressure
sensor due to a change over time. Patent Literature 1 (hereinafter,
PTL 1) discloses a pressure measuring device of such a type.
[0003] The pressure measuring device of PTL 1 is configured to
store, as a learning value of a zero-point learning, an output
value of a pressure sensor, when a drop in the output of the
pressure sensor is stabilized after stopping of the internal
combustion engine.
[0004] Although Patent Literature 2 (hereinafter, PTL 2) does not
mention calibration of the pressure sensor, it discloses a control
device for a diesel engine configured to use an intake air
temperature and a cooling water temperature to determine whether a
throttle valve thereof is frozen.
CITATION LIST
Patent Literature
[0005] PTL 1: Japanese Patent Application Laid-Open No.
2013-125023
[0006] PTL 2: Japanese Patent Application Laid-Open No.
2016-156301
SUMMARY OF INVENTION
Technical Problem
[0007] However, the configuration of the PTL 1 does not take into
account a case of obtaining a calibration reference value when
freezing occurs to the pressure sensor, particularly during winter
in a cold region.
[0008] Meanwhile, the calibration of PTL 2 always uses both the
intake air temperature and the cooling water temperature to
determine whether the throttle valve is frozen, the process of
determination is not necessarily simple.
[0009] The present invention is made in view of the above
circumstances, and it is an object of the present invention to
provide a control device for an internal combustion engine with a
simple process of determination, the control device configured to
obtain a calibration reference value in consideration of freezing
taking place inside the pressure sensor.
Solution to Problem and Advantages
[0010] Problems to be solved by the invention are as described
above, and next, means for solving the problems and effects thereof
will be described.
[0011] In an aspect of the present invention, a control device for
an internal combustion engine having the following configuration is
provided. Namely, the control device for the internal combustion
engine calibrates a detected value from a pressure detection unit
of the internal combustion engine, during operation of the internal
combustion engine. The control device for the internal combustion
engine includes a cooling water temperature detection unit, an
intake air temperature detection unit, a storage unit, a
determination unit, and a calibration unit. The cooling water
temperature detection unit is configured to detect a cooling water
temperature of the internal combustion engine. The intake air
temperature detection unit is configured to detect an intake air
temperature of the internal combustion engine. The storage unit
stores a calibration reference value for calibrating the detection
value from the pressure detection unit. The determination unit
determines whether an environment is a cold environment in which
the pressure detection unit is likely to freeze. The calibration
unit obtains the calibration reference value. In an after-run
control performed after the internal combustion engine stops, the
determination unit compares a cooling water temperature detected by
the cooling water temperature detection unit with a first threshold
value and determines that the environment is not the cold
environment if the cooling water temperature is equal to or higher
than the first threshold. If, as a result of the comparison, the
cooling water temperature detected by the cooling water temperature
detection unit is less than the first threshold value; the
determination unit determines that the environment is not the cold
environment if the cooling water temperature is equal to or higher
than a second threshold value lower than the first threshold value
and the intake air temperature is equal to or higher than a third
threshold value, and otherwise, determines that the environment is
the cold environment. The calibration unit obtains a calibration
reference value based on the detection value from the pressure
detection unit when the determination unit determines that the
environment is not the cold environment. The storage unit stores
the calibration reference value obtained by the calibration
unit.
[0012] With this, the calibration reference value can be obtained
immediately after the internal combustion engine stops, in a
situation where freezing of the pressure detection unit is highly
unlikely. On the other hand, for example, when the internal
combustion engine is stopped very soon after it is started, there
is a possibility of the pressure detection unit being frozen.
Therefore, by determining whether or not the environment is a cold
environment, obtaining of the calibration reference value while the
pressure detection unit is frozen can be suppressed or reduced.
Further, the process of comparing the cooling water temperature
with the threshold values is performed in advance, the process of
determining whether the environment is a cold environment is
simplified. Therefore, sufficiency in the frequency of obtaining
calibration reference value can be achieved.
[0013] The control device for the internal combustion engine is
preferably configured as follows. Namely, when the cooling water
temperature detected by the cooling water temperature detection
unit within a period after powering on and before start of the
internal combustion engine is equal to or higher than a fourth
threshold value, the calibration unit obtains the calibration
reference value based on a detection value detected by the pressure
detection unit within the period after powering on and before start
of the internal combustion engine, and uses the calibration
reference value thus obtained to calibrate detection values of the
pressure detection unit after start of the internal combustion
engine. When the cooling water temperature is less than the fourth
threshold value, the calibration unit uses the calibration
reference value stored in the storage unit, to calibrate detection
values of the pressure detection unit after start of the internal
combustion engine.
[0014] With this, when it is clearly determined that no freezing is
taking place in the pressure detection unit, a detection value
detected by using the pressure detection unit can be used in
calibration, reflecting the current status of the pressure
detection unit. If this is not the case, the calibration reference
value stored in the storage unit is used, so that calibration while
freezing is taking place can be avoided.
BRIEF DESCRIPTION OF DRAWINGS
[0015] FIG. 1 An explanatory diagram schematically showing a flow
of air taken in and exhaust gas in an internal combustion engine
related to one embodiment of the present invention.
[0016] FIG. 2 A block diagram showing a configuration of obtaining
correction values for calibrating an EGR differential pressure
sensor in the ECU.
[0017] FIG. 3 A flowchart used in a process of obtaining the
correction values in an after-run control.
[0018] FIG. 4 A flowchart used in a process of obtaining the
correction values within a period after powering on and before
start of the internal combustion engine.
DESCRIPTION OF EMBODIMENTS
[0019] Next, an embodiment of the present invention will be
described with reference to the drawings. FIG. 1 is an explanatory
diagram schematically showing a flow of air taken in and exhaust
gas in an internal combustion engine 100 related to one embodiment
of the present invention.
[0020] The internal combustion engine 100 shown in FIG. 1 is a
diesel engine, which is configured as a serial four cylinder engine
having four cylinders 30. The internal combustion engine 100
essentially includes an engine body 10 and an ECU (Engine Control
Unit) 90 serving as a control device.
[0021] The engine main body 10 includes, as main parts, an
air-intake unit 2 configured to take in air from the outside,
cylinders 3 each having a not-shown combustion chamber, and an
exhaust unit 4 configured to discharge exhaust gas generated by
combustion of a fuel in the combustion chamber 3 to the
outside.
[0022] The air-intake unit 2 includes an air-intake pipe 21 which
is a passage for the air taken in. The air-intake unit 2 includes a
turbocharger 22, a throttle valve 27, and an air-intake manifold 28
which are arranged in this order from the upstream side relative to
the direction in which the intake air flows in the air-intake pipe
21.
[0023] The air-intake pipe 21 is a passage of the air taken in, and
connects the turbocharger 22, the throttle valve 27, and the
air-intake manifold 28. The air taken in from the outside can flow
inside the air-intake pipe 21.
[0024] As shown in FIG. 1, the turbocharger 22 has a turbine 23, a
shaft 24, and a compressor 25. The compressor 25 is coupled to the
turbine 23 through the shaft 24. The turbine 23 rotates with the
exhaust gas, and with this rotation, the compressor 25 rotates.
This compresses and forcedly sucks in the air cleaned by a
not-shown air cleaner.
[0025] The throttle valve 27 adjusts its opening degree according
to a control command from the ECU 90 thereby changing the
cross-sectional area of the passage for the air taken in. Thus, the
amount of air supplied to the air-intake manifold 28 can be
adjusted through the throttle valve 27.
[0026] The air-intake manifold 28 can distribute the air supplied
through the air-intake pipe 21, according to the number of
cylinders of the engine body 10, thereby supplying the air to the
combustion chamber 3 of each cylinder.
[0027] The air-intake manifold 28 has an intake air temperature
sensor (intake air temperature detection unit) 71. An intake air
temperature Ta detected by the intake air temperature sensor 71 is
output to the ECU 90. It should be noted that the position of
arranging the intake air temperature sensor 71 is not limited to
the air-intake manifold 28, and for example, may be in the intake
air passage on the upstream side of the air-intake manifold 28.
[0028] In the combustion chamber 3, the air supplied through the
air-intake manifold 28 is compressed, and a fuel is injected into
the compressed air whose temperature has risen. This spontaneously
ignites the fuel and pushes the piston to move. The power thus
obtained is transmitted to a suitable device on a power-downstream
side through a not-shown crankshaft and the like.
[0029] The internal combustion engine 100 of the present embodiment
has a not-shown cooling water circulation system. This cooling
water circulation system is configured to recirculate the cooling
water to a cooling jacket formed in a cylinder head or the like of
the engine body 10, to cause heat exchanging for cooling.
[0030] In a suitable position of a cooling water path in the
cooling water circulation system, a cooling water temperature
sensor (cooling water temperature detection unit) 72 for detecting
a cooling water temperature Tw is arranged. The cooling water
temperature Tw detected by the cooling water temperature sensor 72
is output to the ECU 90.
[0031] Further, the internal combustion engine 100 of the present
embodiment includes an atmospheric pressure sensor 73 configured to
detect an atmospheric pressure of the surroundings. For example,
the atmospheric pressure sensor 73 can be provided nearby the ECU
90. The position of arranging the atmospheric pressure sensor 73
can be any position provided that it can detect the atmospheric
pressure.
[0032] The exhaust gas generated by combusting the fuel in the
combustion chamber 3 is discharged from the combustion chamber 3 to
the outside the engine body 10, through the exhaust unit 4.
[0033] The exhaust unit 4 includes an exhaust pipe 41 which is a
passage for the exhaust gas. Further, the exhaust unit 4 includes
an exhaust gas manifold 42 and a DPF (Diesel Particulate Filter) 60
serving as an exhaust gas purification device, which are arranged
in this order from the upstream side relative to the direction in
which the exhaust gas flows in the exhaust pipe 41.
[0034] The exhaust pipe 41 serves as a passage for the exhaust gas
and connects the exhaust gas manifold 42 and the DPF 60. The
exhaust gas discharged from the combustion chamber 3 can flow
inside the exhaust pipe 41.
[0035] The exhaust gas manifold 42 collects the exhaust gas
generated in each combustion chamber 3 and guides the exhaust gas
to the exhaust pipe 41 so as to supply the exhaust gas to the
turbine 23 of the turbocharger 22.
[0036] The DPF 60 serves as an exhaust gas purification device, and
includes an oxidation catalyst 61 and a soot filter 62 for removing
harmful components or particulate matters in the exhaust gas.
Harmful components such as nitrogen monoxide, carbon monoxide, and
the like contained in the exhaust gas are oxidized by the oxidation
catalyst 61. Further, particulate matters contained in the exhaust
gas are collected by the soot filter 62 and are oxidized in the
soot filter 62. As described, the exhaust gas is purified through
the DPF 60.
[0037] Further, the engine body 10 includes an EGR (Exhaust Gas
Recirculation) device 50 and can recirculate part of the exhaust
gas to the air-intake side through the EGR device 50, as shown in
FIG. 1.
[0038] The EGR device 50 includes an EGR pipe 51, an EGR cooler 52,
an EGR valve 53, and an EGR differential pressure sensor 54.
[0039] The EGR pipe 51 is a passage for guiding EGR gas, which is
the exhaust gas recirculated to the air-intake side, to the
air-intake pipe 21, and is arranged in such a manner as to
communicate the exhaust pipe 41 with the air-intake pipe 21.
[0040] The EGR cooler 52 is arranged in a midway portion of the EGR
pipe 51 and cools the EGR gas to be recirculated to the air-intake
side.
[0041] The EGR valve 53 is arranged in a midway portion of the EGR
pipe 51 on the downstream side of the EGR cooler 52 relative to an
EGR gas recirculating direction and can adjust the amount of EGR
gas recirculated. The EGR valve 53 adjusts its opening degree
according to a control signal from the ECU 90, thereby adjusting
the area of recirculation passage for the EGR gas. This way, the
amount of EGR gas recirculated can be adjusted.
[0042] The EGR differential pressure sensor 54 is for detecting the
differential pressure between an intake pressure which is a
pressure of intake air and an exhaust pressure which is a pressure
of the exhaust gas. The EGR differential pressure sensor 54
introduces the intake pressure from the air-intake manifold 28 and
introduces the exhaust pressure from the exhaust gas manifold
42.
[0043] As shown in FIG. 1, the EGR differential pressure sensor 54
includes an exhaust side detection sensor 54a configured to detect
the exhaust pressure introduced, and an intake pressure detection
sensor 54b configured to detect the intake pressure introduced. In
the present embodiment, these two detection sensors 54a and 54b
correspond to the pressure detection unit. The EGR differential
pressure sensor 54 obtains a differential pressure between the
intake pressure and the exhaust pressure based on the detection
values of the two detection sensors 54a and 54b.
[0044] The two detection sensors 54a and 54b output electric
signals according to the pressures. To improve the accuracy of
measurement, each of the detection sensors 54a and 54b performs
detection in advance under the atmospheric pressure. Then, a value
based on an electric signal at this time is stored as a correction
value (a calibration reference value).
[0045] The atmospheric pressure varies depending on the environment
and the like. Given this, in the present embodiment, instead of the
values indicated by the electric signals from the detection sensors
54a and 54b, these values are each converted so that the
atmospheric pressure detected by the atmospheric pressure sensor 73
at that time is the reference, and the value thus converted is
stored as a correction value.
[0046] During a normal measurement, the correction value stored is
read out, and conversion is carried out so that the atmospheric
pressure detected by the atmospheric pressure sensor 73 is the
reference. Then the value indicated by the electric signal from
each of the detection sensors 54a and 54b is calculated such that
the value is zero when it is equal to the value resulting from the
above addition, and a value resulting from this calculation serves
as a detection value. This calculation essentially corresponds to
the zero point adjustment (calibration) of the detection value.
[0047] Therefore, the detection value of each of the detection
sensors 54a and 54b is zero, when it is a pressure that corresponds
to the atmospheric pressure. A difference between the detection
values from the two detection sensors 54a and 54b is a detection
value of the EGR differential pressure sensor 54.
[0048] The ECU 90 controls the opening degree of the EGR valve 53
based on the differential pressure obtained based on the detection
value from the EGR differential pressure sensor 54, and an amount
of recirculation of the EGR gas calculated according to an
operation status of the internal combustion engine 100.
[0049] The following describes with reference to FIG. 2 to FIG. 4
how the correction value for use in calibration of the EGR
differential pressure sensor 54 is obtained.
[0050] FIG. 2 is a block diagram showing a configuration that
obtains a correction value of the EGR differential pressure sensor
in the ECU. FIG. 3 is a flowchart used in a process of obtaining
the correction value in an after-run control. FIG. 4 is a flowchart
used in the process of obtaining the correction values within a
period after powering on and before start of the internal
combustion engine.
[0051] The ECU 90 of the present embodiment is arranged in or
nearby the engine body 10, and includes a determination unit 91, a
zero point adjustment unit (calibration unit) 92, and a storage
unit 93, as shown in FIG. 2. The ECU 90 is configured as a known
computer, and includes a CPU that executes various computation
processes and controls, a ROM, a RAM, and the like which store data
and the like.
[0052] The ECU 90 includes various sensors for detecting the
operational state of the engine body 10. Examples of these sensors
include the above-described intake air temperature sensor 71, the
cooling water temperature sensor 72, the atmospheric pressure
sensor 73, and the like. The ECU 90 uses detection results from
these sensors to control the operation of the engine body 10.
[0053] The determination unit 91 compares at least the cooling
water temperature Tw with a threshold value set in advance to
determine whether the environment is such that freezing is likely
to take place in or around the detection sensors 54a and 54b of the
EGR differential pressure sensor 54.
[0054] The zero point adjustment unit 92 includes a correction
value obtaining unit (calibration reference value obtaining unit)
95, a correction value selection unit 96, and a detection value
calculation unit 97.
[0055] The correction value obtaining unit 95 obtains a correction
value through a calculation, based on pressures indicated by
electric signals from the two detection sensors 54a and 54b of the
EGR differential pressure sensor 54 while the internal combustion
engine 100 is stopped (in other words, while the surroundings of
the detection sensors 54a and 54b are under the atmospheric
pressure), and the atmospheric pressure detected by the atmospheric
pressure sensor 73.
[0056] The correction value selection unit 96 selects, as the
correction value to be used for the detection value calculation
unit 97 to actually calculate the detection value, a correction
value stored in the storage unit 93 which is obtained in the past
by the correction value obtaining unit 95, or a correction value
obtained at the site by the correction value obtaining unit 95.
[0057] During operation of the internal combustion engine 100, the
detection value calculation unit 97 performs the zero point
adjustment to the pressures indicated by the electric signals from
the two detection sensors 54a and 54b of the EGR differential
pressure sensor 54, based on the above correction values, thereby
calculating detection values. Further, the detection value
calculation unit 97 calculates a differential pressure between the
intake pressure and the exhaust pressure, based on the detection
values from the two detection sensors 54a and 54b. The differential
pressure thus obtained is output for controlling the amount of EGR
gas to be recirculated.
[0058] The storage unit 93 includes a non-volatile memory that can
be rewritten. This non-volatile memory can store correction values
obtained by the correction value obtaining unit 95.
[0059] Next, the following describes a case where the zero point
adjustment of the EGR differential pressure sensor 54 becomes
abnormal when the internal combustion engine 100 is operated in a
cold region.
[0060] When the internal combustion engine 100 is left stopped in a
cold region for a long time, the detection sensors 54a and 54b of
the EGR differential pressure sensor 54 or their surroundings may
freeze and a proper correction value cannot be obtained. This is
particularly true in the exhaust side detection sensor 54a, because
the exhaust gas contains water vapor generated by combustion, and
this water vapor is condensed to water and likely to be frozen.
[0061] Specifically, the surroundings of the detection sensors 54a
and 54b may not be the atmospheric pressure, due to ice covering
detection elements of the detection sensors 54a and 54b or ice
clogging an air passage communicating to the detection sensors 54a
and 54b. Such a phenomenon may be hereinafter referred to as
freezing.
[0062] Performing the zero point adjustment using a correction
value obtained under a circumstance where the freezing takes place,
the detection value of the EGR differential pressure sensor 54
becomes abnormal.
[0063] Given this, the ECU 90 of the internal combustion engine 100
of the present embodiment performs a process as described
hereinbelow to avoid an inappropriate zero point adjustment. The
following describes, with reference to FIG. 3 and FIG. 4, a
specific process performed by the ECU 90.
[0064] The flow of FIG. 3 shows a process related to obtaining of a
correction value, in an after-run performed after the rotation of
the internal combustion engine 100 is stopped and before the ECU 90
is powered off.
[0065] When the flow of FIG. 3 starts, the determination unit 91 of
ECU 90 compares the cooling water temperature Tw obtained from the
coolant temperature sensor 72 with a first threshold value T1 (step
S101). This first threshold value T1 is a temperature of the
cooling water such that no freezing is clearly considered as to
take place. For example, the first threshold value T1 can be a
suitable temperature in a range from 40.degree. C. or higher but
not higher than 60.degree. C.
[0066] As a result of the comparison in step S101, if the cooling
water temperature Tw is equal to or higher than the first threshold
value T1, it can be thought that there is no freezing in the two
detection sensors 54a and 54b of the EGR differential pressure
sensor 54. Thus, in this case, the correction value obtaining unit
95 subtract the value of the atmospheric pressure detected by the
atmospheric pressure sensor 73 from the values indicated by the
electric signals from the two detection sensors 54a and 54b under
the atmospheric pressure, and obtains the values resulting from the
subtraction as the correction values (step S102). Then, the
correction value obtaining unit 95 stores the correction values
obtained in the storage unit 93 (step S103), and terminates the
process.
[0067] Regarding the environment surrounding the detection sensors
54a and 54b, an environment such that freezing due to low
temperatures is suspected may be referred to as a cold environment
in the following description. Therefore, step S101 described above
can be rephrased that the determination unit 91 determines whether
the environment is a cold environment based on the cooling water
temperature Tw.
[0068] Meanwhile, as a result of comparison in step S101, if the
cooling water temperature Tw is less than the first threshold value
T1, the determination unit 91 compares the cooling water
temperature Tw with a second threshold value T2 (step S104). The
second threshold value T2 can be a suitable temperature in a range
of, for example, 5.degree. C. or higher but not higher than
10.degree. C.
[0069] A situation where the cooling water temperature Tw is less
than the second threshold value T2 as a result of comparison in
step S104 can be, for example, a case where the internal combustion
engine 100 is started and stopped immediately after in a morning of
a cold region. That is, warming up of the engine is likely
insufficient and the freezing in the detection sensors 54a and 54b
is not solved yet. This, in other words, can be thought that the
current environment is still a cold environment. The correction
values are not obtained in the after-run of this case, and the flow
is terminated.
[0070] On the other hand, if the cooling water temperature Tw is
equal to or higher than the second threshold value T2 as a result
of the comparison in step S104, it is difficult to determine
whether or not the environment is the cold environment, only with
the cooling water temperature Tw. To address this, the
determination unit 91 compares the intake air temperature Ta
detected by the intake air temperature sensor 71 with a third
threshold value T3 (step S105). The third threshold value T3 can be
a suitable temperature in a range of, for example, 5.degree. C. or
higher but not higher than 20.degree. C.
[0071] As a result of comparison in step S105, if the intake air
temperature Ta is equal to or higher than the third threshold value
T3, it can be thought that the two detection sensors 54a and 54b
are not frozen (in other words, not in a cold environment). In this
case, therefore, the correction values are obtained and stored as
is described hereinabove (step S102 and step S103).
[0072] On the other hand, if the intake air temperature Ta is less
than the third threshold value T3 as a result of comparison in step
S105, it is highly unlikely that the freezing in the detection
sensors 54a and 54b is solved. This, in other words, can be said
that the current environment is the cold environment. In this case,
therefore, the correction value is not obtained in this after-run,
and execution of the flow is terminated.
[0073] The flow of FIG. 4 shows a process of selecting the
correction values to be used, which is performed when the power of
the ECU 90 is switched from the OFF state to the ON state.
[0074] When the flow of FIG. 4 starts, the determination unit 91
compares the cooling water temperature Tw obtained from the coolant
temperature sensor 72 with a fourth threshold value T4 (step S201).
As is the case of the above-described first threshold value T1, the
fourth threshold value T4 can be a suitable temperature in a range
of, for example, 40.degree. C. or higher but not higher than
60.degree. C.
[0075] As a result of the comparison in step S201, if the cooling
water temperature Tw is equal to or higher than the fourth
threshold value T4, it can be thought that there is no freezing in
the two detection sensors 54a and 54b, and there is no problem in
obtaining the correction values now. In other words, it can be
considered that the environment is not a cold environment. In view
of this, the correction value obtaining unit 95 obtains the
correction values based on the outputs from the detection sensors
54a and 54b as in step S102 of FIG. 3 (step S202). Then, the
correction value selection unit 96 selects the correction values
obtained in step S202 as the correction values used for the zero
point adjustment (step S203).
[0076] On the other hand, if the cooling water temperature Tw is
less than the fourth threshold value T4, there is a chance of
freezing currently taking place in the detection sensors 54a and
54b. Therefore, the correction value selection unit 96 selects
correction values retrieved from the storage unit 93 as the
correction values to be used for the zero point adjustment (step
S204).
[0077] The correction values selected by either step S203 or step
S204 are used for the detection value calculation unit 97 shown in
FIG. 2 to obtain detection values from electric signals of the
detection sensors 54a and 54b, after the internal combustion engine
100 is started.
[0078] As hereinabove mentioned, freezing may take place in the
detection sensors 54a and 54b of the EGR differential pressure
sensor 54. However, the freezing of the detection sensors 54a and
54b is less likely to take place immediately after the internal
combustion engine 100 is stopped, as compared to a case of leaving
the detection sensors 54a and 54b for a long time after the
stopping of the internal combustion engine 100.
[0079] Therefore, in principle, the correction values are obtained
based on the outputs from the detection sensors 54a and 54b during
the after-run in the present embodiment. The values are then stored
and used in the zero point adjustment, after re-starting of the
engine.
[0080] This way, inappropriate zero point adjustment can be
suppressed or reduced, and an occurrence of abnormality in the
output values of the EGR differential pressure sensor 54 after the
starting of the engine can be avoided.
[0081] However, there is no guarantee that freezing never takes
place during the after-run. For this reason, in the present
embodiment, the determination unit 91 determines whether the
environment is a cold environment during the after-run, and obtains
correction values based on the outputs from the detection sensors
54a and 54b, only when the environment is not a cold environment.
This way, an inappropriate zero point adjustment can be reliably
suppressed or reduced.
[0082] Further, the determination unit 91 determines whether the
environment is a cold environment as follows. Only the temperature
of cooling water whose heat capacity is large is used for
determining whether the environment is not a cold environment or
clearly a cold environment (step S101 and step S104). Next, the
intake air temperature is used for determining whether the
environment is a cold environment (step S105). With this, a highly
reliable determination is achieved. Further, since the logic for
determination becomes simple, the logic can be easily implemented
even in a case where the program volume of the ECU 90 is
limited.
[0083] In the present embodiment, if the environment is clearly not
a cold environment based on the cooling water temperature Tw at the
time of starting the engine, the correction values obtained from
the detection sensors 54a and 54b at the site are used, instead of
the past correction values stored in the storage unit 93 (step S201
to step S203). This way, a zero point adjustment that reflects a
change occurring to the detection sensors 54a and 54b after the ECU
90 is powered off can be performed.
[0084] As hereinabove described, the correction values selected in
step S203 or step S204 are each values resulting from subtracting
the value of the atmospheric pressure detected by the atmospheric
pressure sensor 73 from the values indicated by the electric
signals output from the two detection sensors 54a and 54b under the
atmospheric pressure. Therefore, when the correction values largely
deviate from zero, the detection sensors 54a and 54b are likely to
have an abnormality. In such a case, the ECU 90 generates a
correction value abnormality alarm and restricts the rotation and
the like of the internal combustion engine 100.
[0085] As described, the present embodiment can suppress or reduce
obtaining of the correction values while the detection sensors 54a
and 54b are frozen. Generating of the correction value abnormality
alarm at the time of starting the internal combustion engine 100
can be suppressed or reduced, and the convenience of the internal
combustion engine 100 can be improved.
[0086] As hereinabove described, an ECU 90 of the present
embodiment for an internal combustion engine 100 performs zero
point adjustment to detection values from detection sensors 54a and
54b of an EGR differential pressure sensor 54 provided to the
internal combustion engine 100, while the internal combustion
engine 100 operates. The ECU 90 of the internal combustion engine
includes a cooling water temperature sensor 72, an intake air
temperature sensor 71, a storage unit 93, a determination unit 91,
and a zero point adjustment unit 92. The cooling water temperature
sensor 72 is configured to detect a cooling water temperature Tw of
the internal combustion engine 100. The intake air temperature
sensor 71 is configured to detect an intake air temperature Ta of
the internal combustion engine 100. The storage unit 93 stores
correction values for calibrating detection values from the
detection sensors 54a and 54b. The determination unit 91 determines
whether an environment is a cold environment in which the EGR
differential pressure sensor 54 is likely to freeze. The zero point
correction unit 92 obtains the correction values. In an after-run
control performed after the internal combustion engine 100 stops,
the determination unit 91 compares a cooling water temperature Tw
detected by the cooling water temperature sensor 72 with a first
threshold value T1 (step S101) and determines that the environment
is not the cold environment if the cooling water temperature Tw is
equal to or higher than the first threshold value T1. If, as a
result of the above determination, the cooling water temperature Tw
detected by the cooling water temperature sensor 72 is less than
the first threshold value T1; the determination unit 91 determines
that the environment is not the cold environment if the cooling
water temperature Tw is equal to or higher than a second threshold
value T2 lower than the first threshold value T1 (step S104) and
the intake air temperature Ta is equal to or higher than a third
threshold value T3 (step S105), and otherwise, determines that the
environment is the cold environment. The zero point adjustment unit
92 obtains correction values indicated by the detection sensors 54a
and 54b when the determination unit 91 determines that the
environment is not the cold environment (step S102). The storage
unit 93 stores the correction values obtained by the zero point
correction unit 92 (step S103).
[0087] With this, the correction values for the detection sensors
54a and 54b can be obtained immediately after the internal
combustion engine 100 stops, in a situation where freezing of the
detection sensors 54a and 54b is highly unlikely. On the other
hand, for example, when the internal combustion engine 100 is
stopped very soon after it is started, there is a possibility of
the detection sensors 54a and 54b being frozen. Therefore, by
determining whether or not the environment is a cold environment,
obtaining of the correction values while the detection sensors 54a
and 54b are frozen can be suppressed or reduced. Further, the
process of comparing the cooling water temperature Tw with the
threshold value T1 is performed in advance, the process of
determining whether the environment is a cold environment is
simplified. Therefore, sufficiency in the frequency of obtaining
the correction values can be achieved.
[0088] Further, in the ECU 90 of the internal combustion engine 100
of the present embodiment, when the cooling water temperature Tw
detected by the cooling water temperature sensor 72 within a period
after powering on and before start of the internal combustion
engine 100 is equal to or higher than a fourth threshold value T4,
the zero point adjustment unit 92 obtains the correction values
indicated by electric signals from the detection sensors 54a and
54b, and uses the correction values thus obtained to perform zero
point adjustment of detection values of the detection sensors 54a
and 54b after the internal combustion engine 100 is started (step
S201 to step S203). When the cooling water temperature Tw is less
than the fourth threshold value T4, the zero point adjustment unit
92 uses the correction values stored in the storage unit 93 to
perform zero point adjustment of the detection values of the EGR
differential pressure sensor 54 after powering on of the internal
combustion engine 100 (step S204).
[0089] With this, when it is clearly determined that no freezing is
taking place in the detection sensors 54a and 54b, the correction
values obtained at the site by using the detection sensors 54a and
54b can be used in zero point adjustment, reflecting the current
status of the detection sensors 54a and 54b. If this is not the
case, the correction values stored in the storage unit 93 is used,
so that zero point adjustment while freezing is taking place can be
avoided.
[0090] Although a preferred embodiment of the present invention has
been described above, the above-described configuration can be
modified, for example, as follows.
[0091] The above embodiment deals with a case where the correction
value is obtained and stored during the after-run, for each of the
two detection sensors 54a and 54b. However, since it is the exhaust
side detection sensor 54a in which freezing is likely to take
place, a correction value may be obtained and stored during the
after-run only for the exhaust side detection sensor 54a.
[0092] The storage unit 93 may store correction values having been
obtained by the correction value obtaining unit 95 through a
multiple number of times. This number of times can be suitably set
within a range of, for example, twice or more but not more than ten
times. In this case, for example, if the correction values obtained
in step S204 of FIG. 4 largely deviate from zero, the correction
values previously stored can be retrieved and used.
[0093] In the preparation process for starting the internal
combustion engine 100, the determinations similar to those of step
S101, step S104, step S105 in FIG. 3 may be performed instead of
the determination in step S201 of FIG. 4.
[0094] The above-configuration may be adopted for zero point
adjustment of a pressure sensor other than the detection sensors
54a and 54b of the EGR differential pressure sensor 54.
[0095] The processes shown in the flowcharts of the above
description are no more than examples. The steps in the processes
may be partially modified or deleted, or two or more steps may be
executed in parallel, or another process may be added.
[0096] The above embodiment deals with a four cylinder internal
combustion engine 100 as shown in FIG. 1. However, the number of
cylinders may be a number other than four.
REFERENCE SIGNS LIST
[0097] 71 intake air temperature sensor [0098] 72 cooling water
temperature sensor [0099] 90 ECU [0100] 91 determination unit
[0101] 92 zero point adjustment unit (calibration unit) [0102] 93
storage unit [0103] 100 internal combustion engine [0104] Tw
cooling water temperature [0105] Ta intake air temperature [0106]
T1 first threshold value [0107] T2 second threshold value [0108] T3
third threshold value
* * * * *